Generator-motor

ABSTRACT

A generator-motor includes a control circuit. The control circuit is provided on an end surface of a motor. The control circuit includes a Zener diode, a capacitor, a U-phase arm, a V-phase arm, and a W-phase arm. The Zener diode, the capacitor, the U-phase arm, the V-phase arm, and the W-phase arm are connected in parallel between a positive bus and a negative bus. The Zener diode absorbs a surge voltage applied to the capacitor, the U-phase arm, the V-phase arm, and the W-phase arm.

TECHNICAL FIELD

The present invention relates to a generator-motor attaining a functionas a generator and a motor, that can be reduced in size.

BACKGROUND ART

Japanese Patent Laying-Open No. 2-266855 discloses a starter-generatorattaining a function as a three-phase motor starting an engine mountedon a vehicle and a function as a three-phase AC generator charging abattery.

Referring to FIG. 14, a starter-generator 300 disclosed in JapanesePatent Laying-Open No. 2-266855 includes a motor unit 301 and a driveunit 302. Motor unit 301 includes a stator and a rotor. Drive unit 302is provided on an end surface 301A of motor unit 301. Drive unit 302includes a cylindrical member 302A and a power module 302B. Power module302B is formed on a surface of cylindrical member 302A. That is, powermodule 302B is arranged in a direction perpendicular to a radialdirection 303 of cylindrical member 302A and in a longitudinal direction304 of a rotation shaft 301B of motor unit 301.

Power module 302B feeds a current to a coil included in motor unit 301and drives motor unit 301 so that the rotor outputs a prescribed torque.When the rotor in motor unit 301 rotates by rotation power of an engine,an AC voltage induced in three stators is converted to a DC voltage,whereby a battery is charged.

In this manner, power module 302B is provided on end surface 301A ofmotor unit 301, and drives motor unit 301 as a motor or a generator.

Japanese Patent Laying-Open No. 63-202255 discloses a starter-chargerstarting an engine mounted on a vehicle and charging a battery. FIG. 15is a circuit diagram of the starter-charger disclosed in Japanese PatentLaying-Open No. 63-202255. Referring to FIG. 15, a starter-charger 400includes a battery 310, a key switch 320, a voltage regulator 330, afield coil 340, a crank angle detector 350, an armature currentswitching circuit 360, and an armature coil 380.

Battery 310 outputs a DC voltage. Key switch 320 is connected to an eterminal side at the time of start of the engine (not shown), andconnected to a d terminal side after the start of the engine.

Voltage regulator 330 includes resistors 331 to 333, a Zener diode 334,transistors 335, 337, and a flywheel diode 336. Resistors 331, 332 areconnected in series between a positive bus PLE of battery 310 and aground node GND.

Resistor 333 and transistor 335 are connected in series between the dterminal of key switch 320 and ground node GND. Transistor 335 has thecollector connected to resistor 333 and the base of transistor 337, theemitter connected to ground node GND, and the base connected to Zenerdiode 334.

Zener diode 334 is connected between a node N1 and the base oftransistor 335. Flywheel diode 336 and transistor 337 are connected inseries between positive bus PLE and ground node GND. Transistor 337 hasthe collector connected to one end of field coil 340, the emitterconnected to ground node GND, and the base connected to the collector oftransistor 335.

Flywheel diode 336 absorbs surge produced when transistor 337 opens orcloses.

Field coil 340 has one end connected to the collector of transistor 337and the other end connected to positive bus PLE of battery 310.

With such a circuit configuration, voltage regulator 330 detects a DCvoltage output from battery 310 in a power generation state, andregulates a field current flowing through field coil 340 in order tomaintain a voltage value of the detected DC voltage at a prescribedvalue.

Crank angle detector 350 detects a crank angle between respective phasesof armature coil 380, and outputs the detected crank angle to armaturecurrent switching circuit 360.

Armature current switching circuit 360 includes a current switch controlcircuit 361, N-type MOS transistors 362 to 367, and Zener diodes 368 to373. Current switch control circuit 361 is connected to the e terminalof key switch 320, and receives a crank angle from crank angle detector350. Current switch control circuit 361 is driven by the DC voltage fromthe e terminal so as to generate a signal to turn on/off N-type MOStransistors 362 to 367 based on the crank angle, and outputs thegenerated signal to each of N-type MOS transistors 362 to 367.

N-type MOS transistors 362, 363 are connected in series between positivebus PLE and ground node GND. N-type MOS transistors 364, 365 areconnected in series between positive bus PLE and ground node GND. N-typeMOS transistors 366, 367 are connected in series between positive busPLE and ground node GND.

N-type MOS transistors 362, 363 are connected between positive bus PLEand ground node GND, in parallel to N-type MOS transistors 364, 365 andN-type MOS transistors 366, 367. In addition, N-type MOS transistors362, 364, 366 have respective drain terminals connected to positive busPLE, and have source terminals connected to the drain terminals ofN-type MOS transistors 363, 365, 367 respectively. Moreover, N-type MOStransistors 363, 365, 367 have the drain terminals connected to sourceterminals of N-type MOS transistors 362, 364, 366 respectively, and haverespective source terminals connected to ground node GND.

A node N2 between N-type MOS transistor 362 and N-type MOS transistor363, a node N3 between N-type MOS transistor 364 and N-type MOStransistor 365, and a node N4 between N-type MOS transistor 366 andN-type MOS transistor 367 are connected to different phases of armaturecoil 380 respectively.

Zener diode 368 is connected in parallel to N-type MOS transistor 362,between positive bus PLE and node N2. Zener diode 369 is connected inparallel to N-type MOS transistor 363, between node N2 and ground nodeGND.

Zener diode 370 is connected in parallel to N-type MOS transistor 364,between positive bus PLE and node N3. Zener diode 371 is connected inparallel to N-type MOS transistor 365, between node N3 and ground nodeGND.

Zener diode 372 is connected in parallel to N-type MOS transistor 366,between positive bus PLE and node N4. Zener diode 373 is connected inparallel to N-type MOS transistor 367, between node N4 and ground nodeGND.

With such a circuit configuration, armature current switching circuit360 switches a DC current flowing from battery 310 to armature coil 380.

When the engine is started, key switch 320 is connected to the eterminal. Armature current switching circuit 360 turns on/off N-type MOStransistors 362 to 367 based on the crank angle from crank angledetector 350 and switches the DC current flowing from battery 310 toarmature coil 380, so as to start the engine.

After the engine is started, key switch 320 is connected to the dterminal, and N-type MOS transistors 362 to 367 are all turned off.Starter-charger 300 operates as a generator, and voltage regulator 330regulates a current fed to field coil 340 in order to set a voltagevalue of the DC voltage from battery 310 to a prescribed value. Electricpower generated by armature coil 380 is DC-converted by Zener diodes 368to 373 for charging battery 310.

In this manner, starter-charger 300 drives the engine in starting theengine, and operates as a generator after the engine is started. Even ifsurge produced in cutting off load or surge produced in an ignitionsystem of the engine is applied to armature current switching circuit360, the applied surge flows through Zener diodes 368 to 373. Therefore,N-type MOS transistors 362 to 367 are protected by Zener diodes 368 to373.

In the conventional starter-generator, however, the power module isarranged in a direction perpendicular to a radial direction when therotation shaft is assumed as a center and in a longitudinal direction ofthe rotation shaft. Accordingly, it is difficult to achieve a smallersize of the control circuit controlling drive of the motor.

In addition, the conventional starter-generator has not been able tosufficiently cool the power module.

Moreover, in the conventional starter-charger, the control circuitdriving a motor including the field coil and the armature coil includessix switching elements and six Zener diodes provided corresponding tosix switching elements. Accordingly, if the control circuit driving themotor is provided at an end portion of an alternator, an overall size ofthe control circuit cannot be made smaller.

DISCLOSURE OF THE INVENTION

From the foregoing, an object of the present invention is to provide agenerator-motor including a compact control circuit.

Another object of the present invention is to provide a generator-motorincluding a control circuit occupying a smaller area.

Yet another object of the present invention is to provide agenerator-motor attaining an effect to cool a switching element.

According to the present invention, a generator-motor includes a motorand a control circuit. The motor includes a plurality of coils providedcorresponding to a plurality of phases and attains a function as agenerator-motor. The control circuit controls the motor.

The control circuit includes a plurality of arms and a first Zenerdiode. The plurality of arms are provided corresponding to the pluralityof coils respectively and connected in parallel between a positive busand a negative bus. The first Zener diode is connected in parallel tothe plurality of arms, between the positive bus and the negative bus.

Each of the plurality of arms includes first and second switchingelements and a second Zener diode. The first and second switchingelements are connected in series between the positive bus and thenegative bus. The second Zener diode is connected in parallel to thesecond switching element, between the first switching element and thenegative bus.

Preferably, the control circuit is provided in a manner integrated withthe motor.

Preferably, the motor starts an engine mounted on a vehicle or generateselectric power by a rotation force of the engine.

Preferably, the generator-motor further includes an electronic controlunit. The electronic control unit outputs a control signal to aplurality of first and second switching elements included in the controlcircuit. The first Zener diode is arranged in the vicinity of theelectronic control unit.

Preferably, the generator-motor further includes a fuse. The fuse isprovided closer to a DC power source than to a positive-side connectingposition of the first Zener diode.

According to the present invention, a generator-motor includes a motor,a polyphase switching element group, a control circuit, and first andsecond electrode plates. The motor includes a rotor and a stator, andattains a function as a generator-motor. The polyphase switching elementgroup controls a current supplied to a stator. The control circuitcontrols the polyphase switching element group. The first and secondelectrode plates are arranged on an end surface of the motor so as tosubstantially form a U-shape to surround a rotation shaft of the motor.The control circuit is provided on a ceramic substrate arranged in adirection similar to an inplane direction of the first and secondelectrode plates in a substantially U-shaped notch.

Preferably, the control circuit is resin-molded.

Preferably, the generator-motor further includes a Zener diode. TheZener diode protects the polyphase switching element group againstsurge. The Zener diode is arranged in the notch.

Preferably, the generator-motor further includes a capacitive element.The capacitive element smoothes a DC voltage from a DC power source andsupplies the smoothed DC voltage to the polyphase switching element. Thecapacitive element is arranged between the ceramic substrate and thesecond electrode plate.

Preferably, the generator-motor further includes a field coil controlunit. The field coil control unit controls current feed to the fieldcoil different from the stator. The field coil control unit is arrangedon the ceramic substrate.

Preferably, a leadframe continuing to the first and second electrodeplates from the ceramic substrate and the first and second electrodeplates are provided in an identical plane.

According to the present invention, a generator-motor includes a motor,a plurality of switching elements, and a bus bar. The motor attains afunction as a generator and/or a motor. The plurality of switchingelements control a current supplied to the motor. The bus bar connectsthe plurality of switching elements. A ratio of an area of the bus barto an area of the switching element is five or more.

Preferably, the generator-motor further includes a buffer material. Thebuffer material is provided between the bus bar and the switchingelement and absorbs thermal expansion difference between the bus bar andthe switching element.

Preferably, the buffer material is made of a copper-based oraluminum-based material.

Preferably, the bus bar is made of copper.

Preferably, the bus bar is provided on an end surface of the motor andhas an arc shape.

Preferably, the bus bar includes first to third bus bars. The first busbar implements a power source line. The second bus bar is connected to acoil of the motor. The third bus bar implements a ground line. Theplurality of switching elements include a plurality of first switchingelements and a plurality of second switching elements. The plurality offirst switching elements are provided on the first bus bar. Theplurality of second switching elements are provided on the second busbar. The generator-motor further includes first and second flatelectrodes. The first flat electrode connects the plurality of firstswitching elements to the second bus bar. The second flat electrodeconnects the plurality of second switching elements to the third busbar.

According to the generator-motor of the present invention, the firstZener diode protects the first switching elements included in respectiveones of the plurality of arms. That is, according to the generator-motorof the present invention, one Zener diode protects a plurality ofswitching elements.

Therefore, according to the present invention, a control circuitcontrolling the motor can be made smaller. As a result, the controlcircuit can be provided on the end surface of the motor.

In addition, according to the generator-motor of the present invention,the control circuit controlling drive of the motor attaining a functionas a generator or a motor is arranged in a direction similar to aninplane direction of the first and second electrode plates arranged onthe end surface of the motor. The control circuit is arranged in thesubstantially U-shaped notch in the first and second electrode plates.

Therefore, according to the present invention, an area occupied by thecontrol circuit can be reduced.

Moreover, according to the generator-motor of the present invention, theplurality of switching elements controlling a current fed to the statorof the motor are fixed to the bus bar, with the buffer material composedof a material the same as that for the bus bar being interposed. Then,heat generated in the plurality of switching elements is transmitted tothe bus bar through the buffer-material or both the buffer material andthe flat electrode.

Furthermore, according to the generator-motor of the present invention,a ratio between an area of the bus bar and an area of the switchingelement controlling a current fed to the stator of the motor is set tobe not smaller than 5.

Therefore, according to the present invention, the switching element caneffectively be cooled.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a generator-motor according to the presentinvention.

FIG. 2A is a plan view of a MOS transistor Tr1 shown in FIG. 1.

FIG. 2B is a cross-sectional view of MOS transistor Tr1 and electrodeplates 81, 82A shown in FIG. 1.

FIG. 3 is a cross-sectional view along the line III-III shown in FIG. 1.

FIG. 4 is another cross-sectional view along the line III-III shown inFIG. 1.

FIG. 5 is a cross-sectional view of an area of MOS transistor Tr1 shownin FIG. 1.

FIG. 6 is a cross-sectional view showing a conventional method of fixingan MOS transistor.

FIG. 7 is a plan view for calculating a ratio between an area of anelectrode plate and an area of the MOS transistor.

FIG. 8 shows a relation between increase in an element temperature andbus bar area/element area.

FIG. 9 is a circuit block diagram of the generator-motor and a batteryshown in FIG. 1.

FIG. 10 is another plan view of the generator-motor according to thepresent invention.

FIG. 11A is a plan view of MOS transistor Tr1 shown in FIG. 10.

FIG. 11B is a cross-sectional view of MOS transistor Tr1 and electrodeplates 81, 82A shown in FIG. 10.

FIG. 12 shows a relation between temperature increase of MOS transistorsTr1 to Tr6 shown in FIG. 10 and bus bar area/element area.

FIG. 13 is a schematic block diagram of an engine system including thegenerator-motor shown in FIG. 1.

FIG. 14 is a perspective view of a conventional starter-generator.

FIG. 15 is a circuit diagram of a conventional starter-charger circuit.

BEST MODES FOR CARRYING OUT THE INVENTION

In the following, embodiments of the present invention will be describedin detail with reference to the figures. It is noted that the samereference characters refer to the same or corresponding components inthe figures, and description thereof will not be repeated.

Referring to FIG. 1, a generator-motor 100 according to the presentinvention includes Zener diodes 21, DT1 to DT3, MOS transistors Tr1 toTr6, a power source 26, a MOS driver 27, an alternator 50, a custom IC70, electrode plates 81, 82A to 82C, 83, a substrate 84, terminals 84Ato 84D, and wires 85A to 85D, 86A to 86D.

In the following, description will be provided, assuming thatgenerator-motor 100 is mounted on an automobile adopting what is calledan “eco-run” (an economy running system or an idle stop system) in whichan engine is controlled so as to automatically stop when a vehicle isstopped and is automatically started at the time of re-start of thevehicle.

Electrode plates 81, 82A to 82C, 83 and substrate 84 are formed on anend surface of alternator 50. Electrode plates 81, and 82A to 82C aremade of copper (Cu). Electrode plate 81 has a substantial U-shape(hereinafter, also referred to as an “arc shape”), and is providedaround a rotation shaft 50A of alternator 50. Electrode plates 82A to82C are provided outside electrode plate 81 so as to surround the same.Electrode plates 82A to 82C are arranged at prescribed intervals fromeach other. Electrode plate 83 is arranged in a position at a distancefrom rotation shaft 50A substantially the same as the distance betweenelectrode plates 82A-82C and rotation shaft 50A. A portion of electrodeplate 83 is arranged under electrode plates 82A to 82C. Substrate 84 isarranged in a direction the same as an inplane direction of electrodeplates 81, 82A to 82C, 83 in a substantially U-shaped notch in electrodeplate 81.

MOS transistors Tr1, Tr3, Tr5 are arranged on electrode plate 81, MOStransistor Tr2 and Zener diode DT1 are arranged on electrode plate 82A,MOS transistor Tr4 and Zener diode DT2 are arranged on electrode plate82B, and MOS transistor Tr6 and Zener diode DT3 are arranged onelectrode plate 82C.

MOS transistor Tr1 has the drain connected to electrode plate 81 and thesource connected to electrode plate 82A. MOS transistor Tr2 has thedrain connected to electrode plate 82A and the source connected toelectrode plate 83. Zener diode DT1 has one terminal connected toelectrode plate 82A and the other terminal connected to electrode plate83. Electrode plate 82A is connected to one end 51A of a U-phase coil ofalternator 50.

MOS transistor Tr3 has the drain connected to electrode plate 81 and thesource connected to electrode plate 82B, MOS transistor Tr4 has thedrain connected to electrode plate 82B and the source connected toelectrode plate 83. Zener diode DT2 has one terminal connected toelectrode plate 82B and the other terminal connected to electrode plate83. Electrode plate 82B is connected to one end 52A of a V-phase coil ofalternator 50.

MOS transistor Tr5 has the drain connected to electrode plate 81 and thesource connected to electrode plate 82C. MOS transistor Tr6 has thedrain connected to electrode plate 82C and the source connected toelectrode plate 83. Zener diode DT3 has one terminal connected toelectrode plate 82C and the other terminal connected to electrode plate83. Electrode plate 82C is connected to one end 53A of a W-phase coil ofalternator 50.

Therefore, MOS transistors Tr1, Tr2 are connected in series betweenelectrode plates 81 and 83 through electrode plate 82A. In addition, MOStransistors Tr3, Tr4 are connected in series between electrode plates 81and 83 through electrode plate 82B. Moreover, MOS transistors Tr5, Tr6are connected in series between electrode plates 81 and 83 throughelectrode plate 82C. Electrode plates 82A to 82C are connected to theU-phase coil, the V-phase coil and the W-phase coil of alternator 50,respectively.

Substrate 84 is implemented by a ceramic substrate. Power source 26,custom IC 70, MOS driver 27, and terminals 84A to 84D are arranged onsubstrate 84. Power source 26, custom IC 70, and MOS driver 27 areresin-molded on substrate 84.

Terminal 84A receives a signal M/G and outputs received signal M/G tocustom IC 70 through wire 85A. Terminal 84B receives a signal RLO, andoutputs received signal RLO to custom IC 70 through wire 85B. Terminal84C receives a signal CHGL, and outputs received signal CHGL to customIC 70 through wire 85C. Terminal 84D receives a DC voltage output frombattery 10 and supplies the received DC voltage to power source 26through wire 85D.

In wiring from substrate 84 to electrode plates 81, 82A to 82C, wires86A to 86F are arranged along a circumference surrounding rotation shaft50A in a space between rotation shaft 50A and electrode plate 81. Then,wire 86B is bent at a point C, and extends under electrode plate 81 toreach electrode plate 82A. Wire 86D is bent at a point D, and extendsunder electrode plate 81 to reach electrode plate 82B. In addition, wire86F is bent at a point E, and extends under electrode plate 81 to reachelectrode plate 82C.

MOS driver 27 outputs a control signal to the gates of MOS transistorsTr1 to Tr6 through wires 86A to 86F, respectively.

Zener diode 21 is arranged in a space between substrate 84 and electrodeplates 81, 83, and connected between electrode plates 81 and 83. Acapacitor 22 is arranged in a space between substrate 84 and electrodeplates 81, 82C, 83, and connected between electrode plates 81 and 83.

Electrode plate 81 attains a function as a positive bus which will bedescribed later, and has one end connected to a terminal 87. Electrodeplate 81 receives a DC voltage output from a DC power source throughterminal 87. Electrode plate 83 attains a function as a negative buswhich will be described later.

FIG. 2A is a plan view of MOS transistor Tr1 shown in FIG. 1, and FIG.2B is a cross-sectional view of MOS transistor Tr1 and electrode plates81, 82A shown in FIG. 1. Referring to FIGS. 2A and 2B, MOS transistorTr1 includes a gate G, a source S and a drain D. Gate G is connected towire 86A. Source S is arranged adjacent to gate G, and connected toelectrode plate 82A by a wire GL. Therefore, in order to facilitateconnection of gate G and source S to wire 86A and electrode plate 82Athrough wire GL, respectively, MOS transistor Tr1 is arranged such thatgate G is oriented to a side of rotation shaft 50A and source S isoriented to a side of electrode plate 82A. Drain D is connected toelectrode plate 81.

Each of MOS transistors Tr2 to Tr6 includes a gate G, a source S and adrain D in a manner similar to MOS transistor Tr1, and arrangementthereof is also the same.

In a large power element such as MOS transistors Tr1 to Tr6, in manycases, gate G is provided in a central portion of one side along aperipheral portion of the element as described above, so that a lengthof a signal input line coming from the outside of the element isminimized and so that a pad for an output terminal is made as large aspossible.

Therefore, if drain D of MOS transistors Tr1 to Tr6 is provided on aback surface of the element, wire GL from source S is provided such thatit is drawn out of a side opposite to the side where gate G is present.

If MOS transistors Tr1 to Tr6 are arranged on electrode plates 81, 82A,82B, 82C, in order to attain a shorter length of wires 86A, 86B, 86C,86D, 86E, 86F, GL, MOS transistors Tr1 to Tr6 should be arranged suchthat gate G is oriented to the side of rotation shaft 50A and source Sis oriented to the outer circumferential side.

Then, MOS transistors Tr1, Tr3, Tr5 constitute an upper arm of aninverter controlling a current fed to a coil of each phase of alternator50, while MOS transistors Tr2, Tr4, Tr6 constitute a lower arm of theinverter controlling a current fed to a coil of each phase of alternator50. Accordingly, considering a direction of arrangement of MOStransistors Tr1 to Tr6, arranging electrode plate 81 in an innermostportion and arranging electrode plates 82A, 82B, 82C, 83 outsideelectrode plate 81 is optimal, from a viewpoint of improved efficiencyin cooling MOS transistors Tr1 to Tr6 (arranging MOS transistors Tr1 toTr6 in an inner portion on the end surface of alternator 50 serves tocool MOS transistors Tr1 to Tr6 by a flow of air sucked from outsideinto alternator 50) or a shorter length of wires 86A, 86B, 86C, 86D,86E, 86F, GL.

In addition, it is efficient to arrange electrode plate 83 on anoutermost side, because electrode plate 83 implements a negative bus andcan also be connected to a cover or a frame of alternator 50 forconnection to ground.

For these reasons, electrode plate 81 is arranged in the innermostportion, and electrode plates 82A, 82B, 82C, 83 are arranged outsideelectrode plate 81.

FIG. 3 shows a cross-sectional structure of alternator 50, viewed from across-section along the line III-III shown in FIG. 1. Referring to FIG.3, a rotor 55 is fixed to rotation shaft 50A, and a rotor coil 54 iswound around rotor 55. Stators 56, 57 are fixed on an outer side ofrotor 55, a U-phase coil 51 is wound around stator 56, and V-phase coil52 is wound around stator 57. In FIG. 3, the stator having a W-phasecoil wound is not shown.

Rotation shaft 50A has one end connected to a pulley 160, whichtransmits a torque generated by alternator 50 to a crank shaft of theengine or auxiliary machinery through a belt and in turn transmits therotation power of the crank shaft of the engine to rotation shaft 50A.

On the other end on a side opposite to one end of rotation shaft 50Aconnected to pulley 160, electrode plates 81, 83 are arranged so as tosurround rotation shaft 50A. A brush 58 is arranged so as to be incontact with rotation shaft 50A. Substrate 84 is provided above rotationshaft 50A, and capacitor 22 is arranged in front of substrate 84.

A MOS transistor 40 is provided on a side opposite to capacitor 22, withelectrode plate 81 lying therebetween. MOS transistor 40 has the drainconnected to electrode plate 81 and the source connected to rotor coil54. When alternator 50 generates electric power, a power generationamount is determined depending on a rotor current flowing in rotor coil54. Therefore, MOS transistor 40 feeds rotor coil 54 with a rotorcurrent necessary for alternator 50 to generate an instructed amount ofelectric power.

In this manner, MOS transistor 40 controlling the rotor currentdetermining a power generation amount of alternator 50 is arranged on aback side of substrate 84 when viewed from a direction B.

FIG. 4 is a cross-sectional view showing an arrangement of electrodeplates 81, 82B, 82C, 83 and the like viewed from the cross-section alongthe line III-III shown in FIG. 1. Referring to FIG. 4, wires 86C, 86E,86F are arranged on the left of rotation shaft 50A, and electrode plates81, 82C, 83 are successively arranged toward an outer circumferentialside of wires 86C, 86E, 86F. Here, wires 86C, 86E, 86F and electrodeplates 81, 82C are arranged in an identical plane. Electrode plate 83 isarranged below wires 86C, 86E, 86F and electrode plates 81, 82C, andelectrode plate 83 partially overlaps with electrode plate 82C.

On the right of rotation shaft 50A, wire 86D and electrode plates 81,82B, 83 are successively arranged. A portion of wire 86D and electrodeplates 81, 82B are arranged in an identical plane. Electrode plate 83 isarranged below a portion of wire 86D and electrode plates 81, 82B, andelectrode plate 83 partially overlaps with electrode plate 82B. MOStransistor Tr4 is arranged on electrode plate 82B. Wire 86D is arrangedbetween rotation shaft 50A and electrode plate 81 so as to surroundrotation shaft 50A until it reaches point D (see FIG. 1). After wire 86Dis bent at point D, it extends under electrode plate 81 and is connectedto the gate of MOS transistor Tr4.

FIG. 5 is a cross-sectional view of an area where MOS transistor Tr1shown in FIG. 1 is arranged. Referring to FIG. 5, a buffer material 812is adhered to electrode plate 81 with a solder 811. Then, MOS transistorTr1 is adhered to buffer material 812 with a solder 813. Buffer material812 is made of copper (Cu) or a copper-based material such ascopper-molybdenum or copper-tungsten, and has a thickness in a rangefrom 0.1 to 2.0 mm. That is, buffer material 812 is made of a materialthe same as that for electrode plate 81. Solders 811, 813 are a Pb-free,Ag—Cu—Sn-based solder. Buffer material 812 absorbs a thermal expansiondifference between electrode plate 81 and MOS transistor Tr1. Therefore,even if a temperature is increased due to an operation of MOS transistorTr1 and electrode plate 81 and MOS transistor Tr1 expand, buffermaterial 812 prevents MOS transistor Tr1 from separating from electrodeplate 81.

Referring to FIG. 6, conventionally, a mount portion of MOS transistorTr1 has been constituted of a DBC (Direct Bond Copper) 820 and a heatsink 830 composed of AlSiC/CuMo or the like. DBC 820 is an insulatingsubstrate having such a cross-sectional structure that copper (Cu) 822,823 is formed on opposing sides of ceramics 821. MOS transistor Tr1 hasbeen provided on heat sink 830 with DBC 820 being interposed.Alternatively, MOS transistor Tr1 has been provided on heat sink 830,with DBA (Direct Bond Aluminum) using aluminum (Al) instead of copper(Cu) in DBC 820 being interposed. When MOS transistor Tr1 is provided onheat sink 830 in such a manner, heat generated in MOS transistor Tr1 isless likely to be transmitted to heat sink 830, because ceramics 821 isan insulator. Consequently, MOS transistor Tr1 is not sufficientlycooled.

In contrast, as shown in FIG. 5, when MOS transistor Tr1 is directlyprovided on electrode plate 81 using buffer material 812 made of thematerial the same as that for electrode plate 81, solely metal ispresent between MOS transistor Tr1 and electrode plate 81. In addition,buffer material 812 and electrode plate 81 attain thermal conductivityhigher than MOS transistor Tr1 composed of silicon (Si). Therefore, heatgenerated in MOS transistor Tr1 is likely to be transmitted to electrodeplate 81 serving as the heat sink, and therefore, MOS transistor Tr1 iseffectively cooled.

In this manner, the present invention is characterized in that MOStransistor Tr1 is provided on electrode plate 81 with buffer material812 being interposed, buffer material 812 being made of the material thesame as that for electrode plate 81 or of metal of a similar type. Whenbuffer material 812 is made of the material the same as that forelectrode plate 81 or of metal of a similar type, a thickness thereof iscritical. Specifically, the thickness should be set in a range from 0.1to 2.0 mm as described above, so as to attain a function as a buffermaterial.

Buffer material 812 may not be made of a material the same as that forelectrode plate 81. For example, buffer material 812 may be made ofaluminum (Al) instead of copper (Cu). In addition, buffer material 812may be made of an aluminum-based material. In this case as well, buffermaterial 812 has a thickness in a range from 0.1 to 2.0 mm.

MOS transistors Tr2 to Tr6 are also fixed on electrode plates 81, 82A to82C, in a manner similar to MOS transistor Tr1.

Referring to FIGS. 7 and 8, a ratio between an area of MOS transistorsTr1 to Tr6 and an area of electrode plates 81, 82A to 82C will bedescribed. Referring to FIG. 7, a center of rotation shaft 50A ofalternator 50 is denoted as O, and an angle defined by opposing ends ofelectrode plate 81 and center O is denoted as θ1. In addition, an angledefined by opposing ends of electrode plate 82A and center O is denotedas θ2.

An inner diameter of electrode plate 81 is denoted as D1, while an outerdiameter of electrode plate 81 is denoted as D2. As electrode plates 82Ato 82C are arranged in an arc shape (also referred to as “U shape”) in amanner similar to electrode plate 81, an inner diameter of electrodeplate 82A is denoted as D3, while an outer diameter of electrode plate82A is denoted as D4.

In the present embodiment, a ratio between an area of MOS transistorsTr1 to Tr6 and an area of electrode plates 81, 82A to 82C was found,when MOS transistors Tr1 to Tr6 have a size fixed to 3 mm square, innerdiameter D1 fixed to 40 mm, outer diameter D2 fixed to 70 mm, innerdiameter D3 fixed to 75 mm, and outer diameter D4 fixed to 120 mm, angleθ1 is varied in a range from 80° to 150° while angle θ2 is varied in arange from 70° to 90°, and a temperature of MOS transistors Tr1 to Tr6is not higher than a tolerance limit.

Table 1 shows an area of electrode plates 81, 82A when angle θ1 is setto 84° and angle θ2 is set to 78° as well as an area ratio between MOStransistors Tr1, Tr2 and electrode plates 81, 82A. TABLE 1 (mm²) Element9 * 9 81 (mm²) (times) Bus Bar Diameter 40 Positive electrode 520 6.4 7075 U phase 760 9.4 120

In Table 1, “positive electrode” represents electrode plate 81, while anarea of the positive electrode: 520 mm² represents an area of electrodeplate 81 with respect to one MOS transistor Tr1. Here, the area of thepositive electrode: 520 mm² is comparable to ⅓ of a total area ofelectrode plate 81.

Here, three MOS transistors Tr1, Tr3, Tr5 are provided on electrodeplate 81. Accordingly, unless an area obtained by multiplying the totalarea of electrode plate 81 by ⅓ is used, an accurate ratio between anarea of the electrode plate and an area of one MOS transistor cannot beobtained.

The “U-phase” in Table 1 represents electrode plate 82A.

The ratio between the area of MOS transistors Tr3, Tr5 and the area ofelectrode plate 81 is identical to a value shown with the positiveelectrode in Table 1. The ratio between an area of MOS transistor Tr4and the area of electrode plate 82B as well as the ratio between an areaof MOS transistor Tr6 and the area of electrode plate 82C are identicalto the value shown with the U-phase in Table 1.

The area of electrode plates 81, 82A to 82C is calculated using thevalues described above. If the area of electrode plate 81 is 6.4 timeslarger than the area of MOS transistors Tr1, Tr3, Tr5, the temperatureof MOS transistors Tr1 to Tr6 was not higher than the tolerance limit.

By reducing angle θ1 from 135°, the area of electrode plate 81 becomeslarger. Meanwhile, by increasing angle θ2 from 75°, the area ofelectrode plate 82A becomes larger.

Accordingly, a relation between a ratio of the area of the MOStransistor to the area of the electrode plate and the temperature of MOStransistors Tr1 to Tr6 was examined, by varying angles θ1, θ2 so as tovary the area of electrode plates 81, 82A to 82C.

FIG. 8 shows a relation between increase in a temperature of MOStransistors Tr1 to Tr6 and bus bar area/element area. In FIG. 8, theordinate represents increase in the element temperature, while theabscissa represents the bus bar area/element area. Here, the bus bararea represents the area of electrode plates 81, 82A to 82C. Inaddition, a curve k1 represents a transition state, that is, a motoroperation state, while a curve k2 represents a power generationoperation state.

Referring to FIG. 8, the temperature increase of MOS transistors Tr1 toTr6 is greater in the motor operation state indicated by curve k1 thanin the power generation operation state indicated by curve k2.Therefore, in the present invention, the area of MOS transistors Tr1 toTr6 and the area of electrode plates 81, 82A to 82C are determined suchthat an area ratio not smaller than an area ratio at which thetemperature increase in the element does not exceed the tolerance limitwith respect to k1 is attained. In other words, the area of MOStransistors Tr1 to Tr6 and the area of electrode plates 81, 82A to 82Care determined such that an area ratio (=bus bar area/element area) isnot smaller than 6.

In this manner, heat generated in MOS transistors Tr1 to Tr6 istransmitted to electrode plates 81, 82A to 82C through buffer material812, and MOS transistors Tr1 to Tr6 are cooled so that the temperatureincrease in MOS transistors Tr1 to Tr6 does not exceed the tolerancelimit.

FIG. 9 is a circuit block diagram of generator-motor 100 and battery 10.A control circuit 20 includes Zener diode 21 arranged between substrate84 and electrode plates 81, 83, capacitor 22 arranged between substrate84 and electrode plates 81, 82C, 83, MOS transistors Tr1, Tr3, Tr5arranged on electrode plate 81, MOS transistors Tr2, Tr4, Tr6 arrangedon electrode plates 82A to 82C respectively, power source 26 arranged onsubstrate 84, MOS driver 27, custom IC 70, MOS transistor 40, and adiode 41.

MOS transistors Tr1, Tr2 constitute a U-phase arm 23, MOS transistorsTr3, Tr4 constitute a V-phase arm 24, and MOS transistors Tr5, Tr6constitute a W-phase arm 25.

Custom IC 70 is constituted of a synchronous rectifier 28 and controlunits 29, 30. A rotation angle sensor 60 is contained in alternator 50.

Alternator 50 includes U-phase coil 51, V-phase coil 52, W-phase coil53, and rotor coil 54. U-phase coil 51 has one end 51A connected to anode N1 between MOS transistor Tr1 and MOS transistor Tr2. V-phase coil52 has one end 52A connected to a node N2 between MOS transistor Tr3 andMOS transistor Tr4. W-phase coil 53 has one end 53A connected to a nodeN3 between MOS transistor Tr5 and MOS transistor Tr6.

A fuse FU1 is connected between a positive electrode of battery 10 andcontrol circuit 20. That is, fuse FU1 is arranged on a side of battery10, rather than a side of Zener diode 21. In this manner, by arrangingfuse FU1 on the side of battery 10 rather than the side of Zener diode21, detection of overcurrent is no longer necessary and control circuit20 can be reduced in size. A fuse FU2 is connected between the positiveelectrode of battery 10 and power source 26.

Zener diode 21 and capacitor 22 are connected in parallel between apositive bus L1 and a negative bus L2.

U-phase arm 23, V-phase arm 24, and W-phase arm 25 are connected inparallel between positive bus L1 and negative bus L2. U-phase arm 23consists of MOS transistors Tr1, Tr2 and Zener diode DT1. MOStransistors Tr1, Tr2 are connected in series between positive bus L1 andnegative bus L2. MOS transistor Tr1 has the drain connected to positivebus L1 and the source connected to node N1. MOS transistor Tr2 has thedrain connected to node N1 and the source connected to negative bus L2.Zener diode DT1 is connected in parallel to MOS transistor Tr2, betweennode N1 and negative bus L2.

V-phase arm 24 consists of MOS transistors Tr3, Tr4 and Zener diode DT2.MOS transistors Tr3, Tr4 are connected in series between positive bus L1and negative bus L2. MOS transistor Tr3 has the drain connected topositive bus L1 and the source connected to node N2. MOS transistor Tr4has the drain connected to node N2 and the source connected to negativebus L2. Zener diode DT2 is connected in parallel to MOS transistor Tr4,between node N2 and negative bus L2.

W-phase arm 25 consists of MOS transistors Tr5, Tr6 and Zener diode DT3.MOS transistors Tr5, Tr6 are connected in series between positive bus L1and negative bus L2. MOS transistor Tr5 has the drain connected topositive bus L1 and the source connected to node N3. MOS transistor Tr6has the drain connected to node N3 and the source connected to negativebus L2. Zener diode DT3 is connected in parallel to MOS transistor Tr6,between node N3 and negative bus L2.

Zener diode 40 is connected between the positive electrode of battery 10and a node N4. Diode 41 is connected between node N4 and ground nodeGND.

Here, diodes connected in parallel to MOS transistors Tr1 to Tr6, 40respectively are parasitic diodes formed between MOS transistors Tr1 toTr6, 40 and a semiconductor substrate respectively.

Battery 10 outputs, for example, a DC voltage of 12V. Zener diode 21absorbs a surge voltage generated between positive bus L1 and negativebus L2. In other words, Zener diode 21 absorbs the surge voltage whenthe surge voltage not smaller than a prescribed voltage level is appliedbetween positive bus L1 and negative bus L2, and lowers the DC voltageapplied to capacitor 22 and MOS transistors Tr1 to Tr6 to a level notlarger than the prescribed voltage level. Therefore, it is not necessaryto secure large capacitance of capacitor 22 and large size of MOStransistors Tr1 to Tr6, considering the surge voltage. As a result,capacitor 22 and MOS transistors Tr1 to Tr6 can be reduced in size.

Capacitor 22 smoothes an input DC voltage, and supplies the smoothed DCvoltage to U-phase arm 23, V-phase arm 24, and W-phase arm 25. MOStransistors Tr1 to Tr6 receive a control signal from MOS driver 27 atthe gates, and are turned on/off in accordance with the received controlsignal. Then, MOS transistors Tr1 to Tr6 switch the direct currentflowing in U-phase coil 51, V-phase coil 52, and W-phase coil 53 ofalternator 50 by the DC voltage supplied from capacitor 22, so as todrive alternator 50. In addition, MOS transistors Tr1 to Tr6 convert anAC voltage generated by U-phase coil 51, V-phase coil 52, and W-phasecoil 53 of alternator 50 to the DC voltage in accordance with thecontrol signal from MOS driver 27, so as to charge battery 10.

Zener diodes DT1 to DT3 prevent application of overvoltage to MOStransistors Tr2, Tr4, Tr6 when U-phase coil 51, V-phase coil 52, andW-phase coil 53 of alternator 50 generate electric power, respectively.In other words, Zener diodes DT1 to DT3 protect the lower arm of U-phasearm 23, V-phase arm 24, and W-phase arm 25 when alternator 50 is in apower generation mode.

Power source 26 receives the DC voltage output from battery 10 throughfuse FU2, and supplies the received DC voltage to MOS driver 27 as twoDC voltages having different voltage levels. More specifically, powersource 26 generates, for example, a DC voltage of 5V based on the DCvoltage of 12V received from battery 10, and supplies to MOS driver 27the generated DC voltage of 5V and the DC voltage of 12V received frombattery 10.

MOS driver 27 is driven by the DC voltages of 5V and 12V supplied frompower source 26. Then, MOS driver 27 generates a control signal forturning on/off MOS transistors Tr1 to Tr6 in synchronization with asynchronization signal from synchronous rectifier 28, and outputs thegenerated control signal to the gates of MOS transistors Tr1 to Tr6.More specifically, MOS driver 27 generates the control signal forturning on/off MOS transistors Tr1 to Tr6 in the power generation modeof alternator 50 based on synchronization signals SYNG1 to SYNG6 fromsynchronous rectifier 28, and generates the control signal for turningon/off MOS transistors Tr1 to Tr6 in a drive mode of alternator 50 basedon synchronization signals SYNM1 to SYNM6 from synchronous rectifier 28.

Upon receiving a signal GS from control unit 30, synchronous rectifier28 generates synchronization signals SYNG1 to SYNG6 based on timingsignals TG1 to TG6 from control unit 29, and outputs generatedsynchronization signals SYNG1 to SYNG6 to MOS driver 27. In addition,upon receiving a signal MS from control unit 30, synchronous rectifier28 generates synchronization signals SYNM1 to SYNM6 based on timingsignals TM1 to TM6 from control unit 29, and outputs generatedsynchronization signals SYNM1 to SYNM6 to MOS driver 27.

Control unit 29 receives angles θ3, θ4, θ5 from rotation angle sensor60, and detects the number of revolutions MRN of rotor 55 included inalternator 50 based on received angles θ3, θ4, θ5.

Angle θ3 represents an angle between a direction of magnetic forcegenerated by U-phase coil 51 and a direction of magnetic force generatedby rotor coil 54. Angle θ4 represents an angle between a direction ofmagnetic force generated by V-phase coil 52 and a direction of magneticforce generated by rotor coil 54. Angle θ5 represents an angle between adirection of magnetic force generated by W-phase coil 53 and a directionof magnetic force generated by rotor coil 54. Angles θ3, θ4, θ5periodically vary in a range from 0° to 360°. Therefore, control unit 29detects the number of times that angles θ3, θ4, θ5 periodically vary ina prescribed time period in a range from 0° to 360°, so as to obtain thenumber of revolutions MRN.

Then, control unit 29 detects a timing of voltages Vui, Vvi, Vwi inducedin U-phase coil 51, V-phase coil 52, and W-phase coil 53 of alternator50 based on angles θ3, θ4, θ5, and generates timing signals TG1 to TG6indicating a timing of turn-on/off of MOS transistors Tr1 to Tr6 forconverting voltages Vui, Vvi, Vwi induced in U-phase coil 51, V-phasecoil 52, and W-phase coil 53 to DC voltages based on that detectedtiming.

In addition, control unit 29 generates timing signals TM1 to TM6indicating a timing of turn-on/off of MOS transistors Tr1 to Tr6 forcausing alternator 50 to operate as a drive motor, based on angles θ3,θ4, θ5 and the detected number of revolutions MRN.

Then, control unit 29 outputs generated timing signals TG1 to TG6, TM1to TM6 to synchronous rectifier 28.

Control unit 30 receives signal M/G, signal RLO, and signal CHGL from anexternally provided eco-run ECU (Electrical Control unit) (which will bedescribed later). In addition, control unit 30 receives voltages Vu, Vv,Vw applied to U-phase coil 51, V-phase coil 52, and W-phase coil 53 ofalternator 50.

Control unit 30 determines whether alternator 50 is to operate as agenerator or a drive motor, based on signal M/G. When control unit 30determines that alternator 50 is to operate as the generator, controlunit 30 generates and outputs signal GS to synchronous rectifier 28. Onthe other hand, when control unit 30 determines that alternator 50 is tooperate as the drive motor, control unit 30 determines a manner ofcurrent feed to U-phase coil 51, V-phase coil 52, and W-phase coil 53based on voltages Vu, Vv, Vw, and generates signal MS for drivingalternator 50 in accordance with the determined current feeding manner,for output to synchronous rectifier 28.

In addition, control unit 30 calculates a rotor current in order foralternator 50 to generate an instructed amount of electric power, basedon signal RLO. Control unit 30 generates a signal RCT for feeding thecalculated rotor current to rotor coil 54, and outputs the generatedsignal to the gate of MOS transistor 40.

Moreover, control unit 30 determines which of U-phase arm 23, V-phasearm 24, and W-phase arm 25 has failed based on signal CHGL. If any ofU-phase arm 23, V-phase arm 24, and W-phase arm 25 has failed, controlunit 30 stops the operation of MOS transistors Tr1 to Tr6.

MOS transistor 40 sets the rotor current supplied from battery 10 torotor coil 54 to a prescribed value, based on signal RCT from controlunit 30. Diode 41 prevents a current from flowing from node N4 to groundnode GND. Here, synchronous rectifier 28 and control units 29, 30 areformed as custom IC 70.

Alternator 50 operates either as the drive motor or as the generator.Alternator 50 generates a prescribed torque under the control of controlcircuit 20 at the start of the engine in the drive mode where itoperates as the drive motor, and starts the engine using the generatedprescribed torque. Moreover, alternator 50 generates a prescribed torqueunder the control of control circuit 20 during a period except for startof the engine, and drives driving wheels of the vehicle incorporatinggenerator-motor 100 with the generated prescribed torque. In addition,alternator 50 drives auxiliary machinery using the generated prescribedtorque during a period except for start of the engine.

Meanwhile, alternator 50 generates an AC voltage in accordance with therotor current flowing in rotor coil 54 in the power generation modewhere it operates as the generator, and supplies the generated ACvoltage to U-phase arm 23, V-phase arm 24, and W-phase arm 25.

Rotation angle sensor 60 detects angles θ3, θ4, θ5, and outputs detectedangles θ3, θ4, θ5 to control unit 29.

An overall operation in generator-motor 100 will now be described.Control unit 30 determines whether alternator 50 is to operate as thegenerator or the drive motor, based on signal M/G from the eco-run ECU.When control unit 30 determines that alternator 50 is to operate as thegenerator, control unit 30 generates and outputs signal GS tosynchronous rectifier 28. Control unit 30 generates signal RCT based onsignal RLO from the eco-run ECU, and outputs the generated signal to thegate of MOS transistor 40.

Then, MOS transistor 40 switches the rotor current supplied from battery10 to rotor coil 54 in response to signal RCT. Rotor 55 of alternator 50is rotated by the rotation power of the engine. Then, alternator 50generates a designated amount of electric power and supplies theelectric power to U-phase arm 23, V-phase arm 24, and W-phase arm 25.

On the other hand, upon receiving angles θ3, θ4, θ5 from rotation anglesensor 60, control unit 29 generates timing signals TG1 to TG6, TM1 toTM6 with the method described above based on received angles θ3, θ4, θ5,and outputs the generated timing signal TG1 to TG6, TM1 to TM6 tosynchronous rectifier 28.

Synchronous rectifier 28 generates synchronization signals SYNG1 toSYNG6 in synchronization with timing signals TG1 to TG6 based on signalGS from control unit 30, and outputs the same to MOS driver 27. MOSdriver 27 generates the control signal for turning on/off MOStransistors Tr1 to Tr6 in synchronization with synchronization signalsSYNG1 to SYNG6, and outputs the control signal to the gates of MOStransistors Tr1 to Tr6.

Then, MOS transistors Tr1 to Tr6 are turned on/off by the control signalfrom MOS driver 27, and converts the AC voltage generated by alternator50 to the DC voltage, so as to charge battery 10.

Here, Zener diodes DT1 to DT3 absorb the surge voltage even if the surgevoltage is superposed on the AC voltage generated by alternator 50. Inother words, Zener diodes DT1 to DT3 prevent application of a voltageexceeding a withstand voltage to MOS transistors Tr2, Tr4, Tr6. Inaddition, Zener diode 21 absorbs the surge voltage even if the surgevoltage is superposed on the DC voltage between positive bus L1 andnegative bus L2. In other words, Zener diode 21 prevents application ofthe voltage exceeding the withstand voltage to MOS transistors Tr1, Tr3,Tr5.

When control unit 30 determines that alternator 50 is to be driven asthe drive motor based on signal M/G, control unit 30 determines themanner of current feed to U-phase arm 23, V-phase arm 24, and W-phasearm 25 based on voltages Vu, Vv, Vw, and generates signal MS for drivingalternator 50 in accordance with the determined current feeding manner,for output to synchronous rectifier 28.

Upon receiving angles θ3, θ4, θ5 from rotation angle sensor 60, controlunit 29 generates timing signals TG1 to TG6, TM1 to TM6 with the methoddescribed above based on received angles θ3, θ4, θ5, and outputs thegenerated timing signal TG1 to TG6, TM1 to TM6 to synchronous rectifier28.

Synchronous rectifier 28 generates synchronization signals SYNM1 toSYNM6 in synchronization with timing signals TM1 to TM6 based on signalMS from control unit 30, and outputs the same to MOS driver 27. MOSdriver 27 generates the control signal for turning on/off MOStransistors Tr1 to Tr6 in synchronization with synchronization signalsSYNM1 to SM6, and outputs the same to the gates of MOS transistors Tr1to Tr6.

Then, MOS transistors Tr1 to Tr6 are turned on/off by the control signalfrom MOS driver 27, and switches the current supplied to U-phase arm 23,V-phase arm 24, and W-phase arm 25 of alternator 50 from battery 10 soas to drive alternator 50 as the drive motor. In this manner, alternator50 supplies a prescribed torque to a crank shaft of the engine at thetime of start of the engine, and supplies the prescribed torque to thedriving wheels during a period except for the start of the engine. Inaddition, alternator 50 supplies the prescribed torque to the auxiliarymachinery.

Here, Zener diode 21 absorbs the surge voltage generated betweenpositive bus L1 and negative bus L2 by turning-on/off of MOS transistorsTr1 to Tr6. In other words, Zener diode 21 prevents application of thevoltage exceeding the withstand voltage to MOS transistors Tr1, Tr3,Tr5. In addition, Zener diodes DT1 to DT3 absorb the surge voltage evenif MOS transistors Tr1, Tr3, Tr5 are turned off and the surge voltage isapplied to MOS transistors Tr2, Tr4, Tr6. In other words, Zener diodesDT1 to DT3 prevent application of the voltage exceeding the withstandvoltage to MOS transistors Tr2, Tr4, Tr6.

As described above, MOS transistors Tr1 to Tr6 are arranged on electrodeplates 81, 82A to 82C, 83 provided on the end surface of alternator 50.Such an arrangement is allowed because application of overvoltage to MOStransistors Tr1 to Tr6 is prevented and MOS transistors Tr1 to Tr6 arereduced in size by providing Zener diodes 21, DT1 to DT3. In particular,as one Zener diode 21 protects three MOS transistors Tr1, Tr3, Tr5,Zener diode 21 protecting three MOS transistors Tr1, Tr3, Tr5 can bearranged utilizing a space between substrate 84 and electrode plates 81,83.

In addition, as Zener diode 21 also prevents application of overvoltageto capacitor 22, a capacitance of capacitor 22 can be reduced.Consequently, capacitor 22 can be arranged in a space between substrate84 and electrode plates 81, 82C, 83.

By virtue of these factors, overall control circuit 20 is reduced insize, and control circuit 20 can be arranged on the end surface ofalternator 50. In other words, control circuit 20 can be arranged in aplane perpendicular to rotation shaft 50A, instead of in thelongitudinal direction of rotation shaft 50A of alternator 50. As aresult, an area occupied by control circuit 20 can be reduced.

Since MOS transistors Tr1 to Tr6 are fixed to electrode plates 81, 82Ato 82C with buffer material 812 being interposed, buffer material 812being made of a material the same as that for electrode plates 81, 82Ato 82C, or since a ratio of the area of MOS transistors Tr1 to Tr6 tothe area of electrode plates 81, 82A to 82C is set to not smaller than6, MOS transistors Tr1 to Tr6 can effectively be cooled.

The generator-motor according to the present invention may be agenerator-motor 101 shown in FIG. 10. Referring to FIG. 10, ingenerator-motor 101, though MOS transistors Tr1 to Tr6 are connected toelectrode plates 82A to 82C, 83 by flat electrodes 91 to 96 instead ofwire bonding (W/B) in generator-motor 100 shown in FIG. 1,generator-motor 101 is otherwise the same as generator-motor 100.

Each of flat electrodes 91 to 96 is made of a copper-based material, andhas a thickness in a range from 0.1 to 2.0 mm.

Flat electrode 91 connects the source of MOS transistor Tr1 to electrodeplate 82A. Flat electrode 92 connects the source of MOS transistor Tr2to electrode plate 83. Flat electrode 93 connects the source of MOStransistor Tr3 to electrode plate 82B. Flat electrode 94 connects thesource of MOS transistor Tr4 to electrode plate 83. Flat electrode 95connects the source of MOS. transistor Tr5 to electrode plate 82C. Flatelectrode 96 connects the source of MOS transistor Tr6 to electrodeplate 83.

FIG. 11A is a plan view of MOS transistor Tr1 shown in FIG. 10, whileFIG. 11B is a cross-sectional view of MOS transistor Tr1 and electrodeplates 81, 82A shown in FIG. 10. In FIGS. 11A and 11B, wire GL in FIGS.2A and 2B is replaced with flat electrode 91, however, FIGS. 11A and 11Bare otherwise the same as FIGS. 2A and 2B.

Flat electrode 91 connects source S of MOS transistor Tr1 to electrodeplate 82A. Flat electrode 91 is connected to source S of MOS transistorTr1 and to electrode plate 82A by soldering. Here, a Pb-free,Ag—Cu—Sn-based solder is employed. The solder attains thermalconductivity two times higher than a normal solder. Accordingly, heatgenerated in MOS transistor Tr1 can efficiently be conducted to flatelectrode 91 and electrode plate 82A, and heat dissipation effect of MOStransistor Tr1 can be enhanced.

Source S is preferably composed of Al—Ni—Au. Here, aluminum (Al) isformed so as to be in contact with silicon (Si) used as a material forMOS transistor Tr1. That is, source S is fabricated by successivelydepositing aluminum (Al), nickel (Ni) and gold (Au) on MOS transistorTr1 (Si). In this manner, adhesion between flat electrode 91 and sourceS of MOS transistor Tr1 in soldering flat electrode 91 to source S ofMOS transistor Tr1 can be improved. It is noted that gate G may also befabricated with Al—Ni—Au, in a manner similar to source S. In addition,source S and gate G may be fabricated with Al—Ni.

The solder the same as that used in connecting flat electrode 91 tosource S of MOS transistor Tr1 and to electrode plate 82A is employed,also when flat electrode 92 is connected to source S of MOS transistorTr2 and electrode plate 83, when flat electrode 93 is connected tosource S of MOS transistor Tr3 and electrode plate 82B, when flatelectrode 94 is connected to source S of MOS transistor Tr4 andelectrode plate 83, when flat electrode 95 is connected to source S ofMOS transistor Tr5 and electrode plate 82C, and when flat electrode 96is connected to source S of MOS transistor Tr6 and electrode plate 83.Otherwise, the description in connection with FIGS. 2A and 2B is alsoapplicable here.

MOS transistors Tr2 to Tr6 shown in FIG. 10 are also connected toelectrode plates 82B, 82C, 83 by flat electrodes 92 to 96 respectively,in a manner similar to MOS transistor Tr1.

In this manner, in generator-motor 101, MOS transistors Tr1 to Tr6 areconnected to electrode plates 82A, 83, 82B, 83, 82C, 83 by flatelectrodes 91 to 96, respectively.

FIG. 12 shows a relation between temperature increase of MOS transistorsTr1 to Tr6 shown in FIG. 10 and the bus bar area/element area. In FIG.12, curves k1, k2 represent a relation between temperature increase ofMOS transistors Tr1 to Tr6 and the bus bar area/element area when MOStransistors Tr1 to Tr6 are connected to electrode plates 82A, 82B, 82C,83 through wire GL, while curves k3, k4 represent a relation betweentemperature increase of MOS transistors Tr1 to Tr6 and the bus bararea/element area when MOS transistors Tr1 to Tr6 are connected toelectrode plates 82A, 82B, 82C, 83 through flat electrodes 91 to 96.Curve k3 represents a transition state, that is, a motor operationstate, while curve k4 represents a power generation operation state.Description on curves k1, k2 has already been provided in connectionwith FIG. 8.

Referring to FIG. 12, by connecting MOS transistors Tr1 to Tr6 toelectrode plates 82A, 82B, 82C, 83 through flat electrodes 91 to 96,temperature increase of MOS transistors Tr1 to Tr6 in the motoroperation state can be reduced by approximately 35% (see curves k1, k3).In addition, temperature increase of MOS transistors Tr1 to Tr6 in thepower generation operation state can be reduced by 3 to 6% (see curvesk2, k4).

In an area not larger than the tolerance limit of the temperatureincrease in the element, the temperature increase of MOS transistors Tr1to Tr6 is greater in the power generation operation state indicated bycurve k4 than in the motor operation state indicated by curve k3.Therefore, in the present invention, when flat electrodes 91 to 96 areemployed, the area of MOS transistors Tr1 to Tr6 and the area ofelectrode plates 81, 82A to 82C are determined such that an area rationot smaller than an area ratio at which the temperature increase in theelement indicated by curve k4 does not exceed the tolerance limit isattained. In other words, the area of MOS transistors Tr1 to Tr6 and thearea of electrode plates 81, 82A to 82C are determined such that an arearatio (=bus bar area/element area) is not smaller than 5.

In this manner, heat generated in MOS transistors Tr1 to Tr6 istransmitted to electrode plates 81, 82A to 82C through buffer material812 and flat electrodes 91 to 96, and MOS transistors Tr1 to Tr6 arecooled so that the temperature increase of MOS transistors Tr1 to Tr6does not exceed the tolerance limit.

In this manner, when MOS transistors Tr1 to Tr6 are connected toelectrode plates 82A, 83, 82B, 83, 82C, 83 by flat electrodes 91 to 96respectively, heat generated in MOS transistors Tr1 to Tr6 is dissipatedthrough flat electrodes 91 to 96. As a result, when MOS transistors Tr1to Tr6 are connected to electrode plates 82A to 82C, 83 by wire bonding(W/B) as in generator-motor 100, a ratio between the area of electrodeplates 81, 82A to 82C and the area of MOS transistors Tr1 to Tr6 shouldbe set to not smaller than 6 in order to cool MOS transistors Tr1 to Tr6so that temperature increase in MOS transistors Tr1 to Tr6 is not largerthan the tolerance limit. On the other hand, when MOS transistors Tr1 toTr6 are connected to electrode plates 82A to 82C, 83 by flat electrodes91 to 96 respectively as in generator-motor 101, a ratio between thearea of electrode plates 81, 82A to 82C and the area of MOS transistorsTr1 to Tr6 for cooling MOS transistors Tr1 to Tr6 so that temperatureincrease in MOS transistors Tr1 to Tr6 is not larger than the tolerancelimit can be set to 5, which is smaller than 6.

Accordingly, if an area for MOS transistors Tr1 to Tr6 is constant, anarea for electrode plates 81, 82A to 82C can be made smaller byconnecting MOS transistors Tr1 to Tr6 to electrode plates 82A to 82C, 83using flat electrodes 91 to 96 respectively.

FIG. 13 shows a block diagram of an engine system 200 includinggenerator-motor 100 shown in FIG. 1. Referring to FIG. 13, engine system200 includes battery 10, control circuit 20, alternator 50, an engine110, a torque converter 120, an automatic transmission 130, pulleys 140,150, 160, a belt 170, auxiliary machinery 172, a starter 174, anelectrohydraulic pump 180, a fuel injection valve 190, an electric motor210, a throttle valve 220, an eco-run ECU 230, en engine ECU 240, and aVSC (Vehicle Stability Control)-ECU 250.

Alternator 50 is arranged proximate to engine 110. Control circuit 20 isarranged on the end surface of alternator 50, as described above.

Engine 110 is started by alternator 50 or starter 174, and generates aprescribed output power. More specifically, engine 110 is started byalternator 50 at a start after stop in accordance with the economyrunning system (also referred to as “eco-run”), while engine 110 isstarted by starter 174 at the time of start using an ignition key.Engine 110 provides the generated output power from a crank shaft 110 ato torque converter 120 or pulley 140.

Torque converter 120 transmits rotation of engine 110 from crank shaft110 a to automatic transmission 130. Automatic transmission 130 exertsautomatic transmission control, sets the torque from torque converter120 to a torque in accordance with transmission control, and providesthe torque to an output shaft 130 a.

Pulley 140 is connected to crank shaft 110 a of engine 110. Pulley 140operates together with pulleys 150, 160 via belt 170.

Belt 170 links pulleys 140, 150, 160 with each other. Pulley 150 isconnected to a rotation shaft of auxiliary machinery 172.

Pulley 160 is connected to the rotation shaft of alternator 50, andturned by crank shaft 110 a of engine 110 or alternator 50.

Auxiliary machinery 172 is implemented by one or more of a compressorfor air-conditioner, a power steering pump, and an engine-cooling waterpump. Auxiliary machinery 172 receives the output power from alternator50 through pulley 160, belt 170 and pulley 150, and is driven by thereceived output power.

Alternator 50 is driven by control circuit 20. Alternator 50 receivesthe rotation power of crank shaft 110 a of engine 110 through pulley140, belt 170 and pulley 160, and converts the received rotation powerto electric energy. In other words, alternator 50 generates electricpower by the rotation power of crank shaft 110 a. Here, alternator 50generates electric power in the following two cases. That is, alternator50 generates electric power when it receives the rotation power of crankshaft 110 a produced by drive of engine 110 in a normal running state ofa hybrid vehicle equipped with engine system 200. In addition, thoughengine 110 is not driven, alternator 50 generates electric power uponreceiving the rotation power transmitted to crank shaft 110 a from thedriving wheels in deceleration of the hybrid vehicle.

Alternator 50 is driven by control circuit 20, and outputs a prescribedoutput power to pulley 160. The prescribed output power is transmittedto crank shaft 110 a of engine 110 through belt 170 and pulley 140 whenengine 110 is started, or it is transmitted to auxiliary machinery 172through belt 170 and pulley 150 in driving auxiliary machinery 172.

Battery 10 supplies the DC voltage of 12V to control circuit 20, asdescribed above.

Control circuit 20 converts the DC voltage from battery 10 to the ACvoltage under the control of eco-run ECU 230 as described above, anddrives alternator 50 using the obtained AC voltage. In addition, controlcircuit 20 converts the AC voltage generated by alternator 50 to the DCvoltage under the control of eco-run ECU 230, and charges battery 10using the obtained DC voltage.

Starter 174 starts engine 110 under the control of eco-run ECU 230.Electrohydraulic pump 180 is contained in automatic transmission 130,and supplies a hydraulic fluid to a hydraulic control unit provided inautomatic transmission 130 under the control of engine ECU 240. Thehydraulic fluid serves to adjust an actuation state of a clutch, a brakeand a one-way clutch within automatic transmission 130 by means of acontrol valve in the hydraulic control unit, so as to switch a shiftstate as required.

Eco-run ECU 230 serves for mode control of alternator 50 and controlcircuit 20, control of starter 174, and control of an amount of powerstorage in battery 10. Here, the mode control of alternator 50 andcontrol circuit 20 refers to control of the power generation mode inwhich alternator 50 attains a function as the generator and the drivemode in which alternator 50 attains a function as the drive motor. Here,a control line from eco-run ECU 230 to battery 10 is not shown.

In addition, eco-run ECU 230 detects the number of revolutions MRN basedon angles θ1, θ2, θ3 from rotation angle sensor 60 contained inalternator 50, whether or not the eco-run system has been started by adriver through an eco-run switch, and other data.

Fuel injection valve 190 controls injection of a fuel under the controlof engine ECU 240. Electric motor 210 controls an opening position ofthrottle valve 220 under the control of engine ECU 240. Throttle valve220 is set to a prescribed opening position by electric motor 210.

Engine ECU 240 serves for control of turn-on/off of auxiliary machinery172 except for the engine-cooling water pump, control of drive ofelectrohydraulic pump 180, transmission control of automatictransmission 130, control of injection of a fuel by fuel injection valve190, control of the opening position of throttle valve 220 by electricmotor 210, and other engine control.

In addition, engine ECU 240 detects a temperature of engine-coolingwater from a temperature sensor, whether or not an accelerator pedal hasbeen pressed down from an idle switch, a degree of press-down of theaccelerator from an accelerator press-down degree sensor, a steeringwheel angle from a steering wheel angle sensor, a vehicle speed from avehicle speed sensor, a throttle opening position from a throttleopening position sensor, a shift position from a shift position sensor,the number of revolutions of the engine from an engine speed sensor,whether or not an operation to turn on/off of the air-conditioner hasbeen performed from a switch of the air-conditioner, and other data.

VSC-ECU 250 detects whether or not a brake pedal has been pressed downfrom a brake switch, and other data.

Eco-run ECU 230, engine ECU 240 and VSC-ECU 250 mainly include amicrocomputer, in which a CPU (Central Processing Unit) executes anecessary operation in accordance with a program written in an internalROM (Read Only Memory) and a variety of types of control are appliedbased on a result of the operation. The result of the operation anddetected data can be communicated as data, among eco-run ECU 230, engineECU 240 and VSC-ECU 250. Therefore, the data can be exchanged asrequired, and control can be applied in a cooperative manner.

Engine system 200 should operate so as to exert already-known idle stopcontrol. More specifically, the engine is stopped by detectingdeceleration or stop of the vehicle based on outputs from a variety ofsensors, and the engine is started by alternator 50 when the driverintends start (such an intention can be detected based on a status ofoperation of the brake or the accelerator pedal). In engine system 200,control circuit 20 controlling alternator 50 is provided on the endsurface of alternator 50, and drives alternator 50 as the drive motor oras the generator in accordance with the instruction from eco-run ECU230. In driving alternator 50 as the drive motor or as the generator,heat generated by MOS transistors Tr1 to Tr6 in control circuit 20 istransmitted to electrode plates 81, 82A to 82C through buffer material812, so that MOS transistors Tr1 to Tr6 are effectively cooled.

Here, it goes without saying that generator-motor 101 is applicable toengine system 200.

In the present invention, alternator 50 includes the stator and therotor, and implements a “motor” attaining a function as themotor-generator.

In addition, in the present invention, electrode plates 81, 82A to 82C,83 implement “bus bars”.

Moreover, in the present invention, electrode plate 81 implements a“first bus bar,” electrode plates 82A to 82C implement “second busbars,” and electrode plate 83 implements a “third bus bar.”

Furthermore, in the present invention, MOS driver 27, synchronousrectifier 28 and control units 29, 30 constitute an “electronic controlunit.”

In the present invention, MOS transistor 40 implements a “field coilcontrol unit” controlling current feed to the field coil different fromthe stator.

In addition, in the present invention, MOS transistors Tr1 to Tr6constitute a “polyphase switching element group” controlling a currentto be fed to the stator.

Furthermore, in the present invention, wires 86A to 86F constitute a“leadframe” extending from substrate 84 (implemented by a ceramicsubstrate) to electrode plates 81, 82A to 82C, 83.

In the generator-motor according to the present invention, a ratiobetween the element area and the bus bar area (bus bar area/elementarea) should be set to not smaller than 5.

According to the embodiment of the present invention, in thegenerator-motor, the plurality of switching elements controlling acurrent to be fed to the coil of the alternator attaining the functionas the generator and the drive motor are fixed to the electrode platewith the buffer material being interposed, the buffer material beingmade of the material the same as that for the electrode plate to whichthe plurality of switching elements are fixed. Therefore, the pluralityof switching elements can effectively be cooled.

In addition, according to the embodiment of the present invention, inthe generator-motor, the ratio of the area of the electrode plate towhich the plurality of switching elements are fixed to the area of eachof the plurality of switching elements controlling the current to be fedto the coil of the alternator attaining the function as the generatorand the drive motor has been set to not smaller than 5. Accordingly, theplurality of switching elements can effectively be cooled.

Moreover, according to the embodiment of the present invention, thecontrol circuit controlling drive of the alternator attaining thefunction as the generator or the motor includes the plurality ofswitching elements and one Zener diode preventing application of thesurge voltage to the plurality of switching elements. Accordingly, atotal size of the control circuit can be made smaller. Consequently, thecontrol circuit can be provided on the end surface of the alternator.

Furthermore, according to the embodiment of the present invention, thegenerator-motor includes a polyphase switching element group controllingthe current to be fed to the coil of the alternator attaining thefunction as the generator or the motor, a control circuit controllingthe polyphase switching element group, and two electrode plates providedso as to substantially form a U-shape to surround the rotation shaft ofthe alternator. The control circuit is provided on the ceramic substratearranged in the inplane direction of the two electrode plates in thesubstantially U-shaped notch. Accordingly, the area occupied by thecontrol circuit can be reduced, and consequently, the generator-motorcan be reduced in size.

In the present embodiment, though the eco-run ECU and the engine ECUhave separately been provided, one engine control ECU can be implementedby integrating their functions. Moreover, the transmission in thepresent embodiment is not limited to AT (what is called an automatictransmission), and it can be implemented by a combination of knowntransmissions such as a CVT and an MT.

Furthermore, the present embodiment is applicable to a hybrid vehicle inwhich the motor is able to generate a large driving force in spite ofbeing adapted to the eco-run system. The present invention can beachieved even if alternator 50 is replaced by another well-knowngenerator-motor (also referred to as the motor-generator). That is, agenerator-motor capable of applying a torque necessary for driving thevehicle or starting the engine should only be selected as appropriate.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a generator-motor that can bereduced in size.

1. A generator-motor, comprising: a motor including a plurality of coilsprovided corresponding to a plurality of phases and attaining a functionas a motor-generator; and a control circuit controlling said motor;wherein said control circuit includes a plurality of arms providedcorresponding to said plurality of coils respectively and connected inparallel between a positive bus and a negative bus, and a first Zenerdiode connected in parallel to said plurality of arms, between saidpositive bus and said negative bus, and each of said plurality of armsincludes first and second switching elements connected in series betweensaid positive bus and said negative bus, and a second Zener diodeconnected in parallel to said second switching element, between saidfirst switching element and said negative bus.
 2. The generator-motoraccording to claim 1, wherein said control circuit is provided in amanner integrated with said motor.
 3. The generator-motor according toclaim 1, wherein said motor starts an engine mounted on a vehicle orgenerates electric power by a rotation force of said engine.
 4. Thegenerator-motor according to claim 1, further comprising an electroniccontrol unit outputting a control signal to a plurality of first andsecond switching elements included in said control circuit, wherein saidfirst Zener diode is arranged in vicinity of said electronic controlunit.
 5. The generator-motor according to claim 1, further comprising afuse provided closer to a DC power source than to a positive-sideconnecting position of said first Zener diode.
 6. A generator-motor,comprising: a motor including a rotor and a stator and attaining afunction as a motor-generator; first and second electrode platesarranged on an end surface of said motor so as to substantially form aU-shape to surround a rotation shaft of said motor; a polyphaseswitching element group controlling a current supplied to said stator;and a control circuit controlling said polyphase switching elementgroup; wherein said control circuit is provided on a ceramic substratearranged in a direction similar to an inplane direction of said firstand second electrode plates in a substantially U-shaped notch.
 7. Thegenerator-motor according to claim 6, wherein said control circuit isresin-molded.
 8. The generator-motor according to claim 6, furthercomprising a Zener diode protecting said polyphase switching elementgroup against surge, wherein said Zener diode is arranged in said notch.9. The generator-motor according to claim 6, further comprising acapacitive element smoothing a DC voltage from a DC power source andsupplying the smoothed DC voltage to said polyphase switching elementgroup, wherein said capacitive element is arranged between said ceramicsubstrate and said second electrode plate.
 10. The generator-motoraccording to claim 6, further comprising a field coil control unitcontrolling current feed to a field coil different from said stator,wherein said field coil control unit is arranged on said ceramicsubstrate.
 11. The generator-motor according to claim 6, wherein aleadframe continuing to said first and second electrode plates from saidceramic substrate and said first and second electrode plates arearranged in an identical plane.
 12. A generator-motor, comprising: amotor attaining a function as a generator-motor; a plurality ofswitching elements controlling a current supplied to said motor; and abus bar connecting said plurality of switching elements; wherein a ratioof an area of said bus bar to an area of said switching element is atleast five.
 13. The generator-motor according to claim 12, furthercomprising a buffer material provided between said bus bar and saidswitching element and absorbing thermnal expansion difference betweensaid bus bar and said switching element.
 14. The generator-motoraccording to claim 12, wherein said buffer material is made of acopper-based or aluminum-based material.
 15. The generator-motoraccording to claim 12, wherein said bus bar is made of copper.
 16. Thegenerator-motor according to claim 12, wherein said bus bar is providedon an end surface of said motor and has an arc shape.
 17. Thegenerator-motor according to claim 12, wherein said bus bar includes afirst bus bar implementing a power source line, a second bus barconnected to a coil of said motor, and a third bus bar implementing aground line, said plurality of switching elements include a plurality offirst switching elements provided on said first bus bar, and a pluralityof second switching elements provided on said second bus bar, and saidgenerator-motor further comprises a plurality of first flat electrodesconnecting said plurality of first switching elements to said second busbar, and a plurality of second flat electrodes connecting said pluralityof second switching elements to said third bus bar.